Method of using a sulfur-tolerant catalyst

ABSTRACT

Disclosed in certain embodiments is a sulfur tolerant catalytic system that includes a catalytic material coated onto a substrate. Certain embodiments are directed to a method of preparing a sulfur-tolerant catalyst.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. Non-Provisionalapplication Ser. No. 15/756,432, filed on Feb. 28, 2018, which is anational phase filing of International Application No.PCT/US2016/052832, filed on Sep. 21, 2016, which claims the benefit ofpriority of U.S. Provisional Application No. 62/221,797, filed Sep. 22,2015. The contents of these applications are hereby incorporated byreference herein in their entireties.

FIELD OF THE INVENTION

The present invention relates to a sulfur tolerant oxidation catalyticsystem, methods of manufacturing, and methods of use for such catalyticsystems in power generation, mobile, or stationary source exhaustapplications containing CO, HCs, VOCs, ozone, NOx, or other compounds.

BACKGROUND OF THE INVENTION

Sulfur compounds in natural gas may have a deleterious effect onoxidation catalysts used to treat exhaust gas from power generationturbines. The levels and types of sulfur compounds found in natural gasmay vary due to source region, mercaptans used for odorants, andincreased use of hydraulic fracturing. In particular, alumina basedcatalysts have been known to quickly deactivate in high sulfur exhaustgases due to aluminum sulfate formation and subsequent loss of catalystcarrier surface area.

The need for a sulfur tolerant catalyst that can maintain its activityin the long term still remains due to market pressures for increasedcost savings in the power generation industry and the unexpected highsulfur levels in exhaust streams. Such a sulfur tolerant catalyst willprovide the power generation operator with peace of mind, more incomewhile operating at high efficiency conditions, and less downtime due tocatalyst washing and replacement.

Efforts to create sulfur tolerant oxidation catalysts using a variety ofmethods have been previously described, including adding a bismuthcompound to the catalytic system to inhibit the production of sulfurtrioxide compounds (which are known for their catalyst poisoningpropensity) and applying multiple washcoat layers of varying platinumand palladium ratios to boost sulfur tolerance. Nevertheless, therecontinues to be a need for methods and compositions for asulfur-tolerant oxidation catalyst that can maintain long term efficacyand performance despite unexpected high sulfur level conditions.

SUMMARY

It is an object of certain embodiments of the disclosure to provide acatalytic system that is sulfur tolerant.

It is an object of certain embodiments of the disclosure to provide amethod for preparing a sulfur tolerant catalytic system.

It is an object of certain embodiments of the disclosure to provide amethod of controlling carbon monoxide levels in an exhaust gas streamcontaining high sulfur levels.

It is an object of certain embodiments of the disclosure to provide amethod of controlling carbon monoxide levels in an exhaust gas streamdevoid of sulfur.

The above objects and others are met by the present disclosure, which incertain embodiments is directed to a catalytic system comprising acatalytic material and a substrate, wherein the catalytic material iscoated on the substrate. In certain embodiments, the catalytic materialcomprises an active precious metal component and a sulfur-tolerantsupport material. In certain embodiments, the active precious metalcomponent comprises platinum, palladium, or mixtures thereof and thesulfur-tolerant support material comprises a mixture of silica andzirconia.

In certain embodiments, the disclosure is directed to a sulfur-tolerantcatalytic system comprising a catalytic material, comprising an activeprecious metal component, comprising platinum, palladium, or a mixturethereof, wherein platinum may be present in an amount ranging from 0.4wt % to 5.0 wt % based of a total weight of the catalytic material andthe palladium may be present in an amount up to 5.0 wt % based of atotal weight of the catalytic material, and a sulfur-tolerant supportmaterial may be present in an amount ranging from 90 wt % to 98 wt %based of a total weight of the catalytic material, and a substrate,wherein the catalytic material may be coated on the substrate.

In certain embodiments, the sulfur-tolerant catalytic system may furthercomprise bulk ceria, which may be present in an amount ranging from 0.5wt % to 10 wt % based on a total weight of the catalytic material. Thecatalytic system may further comprise alumina, which may be present inan amount of up to 10 wt % based on a total weight of the catalyticmaterial.

In certain embodiments, the substrate of the sulfur-tolerant catalyticsystem may comprise a ceramic material or a metal foil. In certainembodiments, the catalytic material may be washcoated on the substrate.

In certain embodiments, the sulfur-tolerant catalytic system comprisesparticles of catalytic material, comprising an active precious metalcomponent and a sulfur-tolerant support, and a substrate, wherein theparticles of catalytic material are washcoated on the substrate and the90% cumulative undersize particles of catalytic material may be, forexample, from about 6 micrometers to about 14 micrometers, or about 10micrometers.

In certain embodiments, the disclosure is directed to a method ofpreparing a sulfur-tolerant catalytic system that may obtain a carbonmonoxide conversion greater than 80% after continuous long termoperation under high sulfur level conditions.

In certain embodiments, the method of preparing a sulfur-tolerantcatalytic system comprises: impregnating an active precious metalsolution, comprising platinum, palladium, or a mixture thereof, onto asulfur tolerant support material, comprising a mixture of silicon andzirconium oxides, to form a slurry; coating a substrate, comprising aceramic material or a metal foil, with the slurry; drying the coatedsubstrate; and calcining the coated substrate, to prepare asulfur-tolerant catalytic system that may obtain a carbon monoxideconversion greater than 80% after continuous long term operation underhigh sulfur level conditions.

In certain embodiments, the method of preparing a sulfur tolerantcatalytic system comprises: coating a substrate, comprising a ceramicmaterial or a metal foil, with a sulfur-tolerant support material,comprising a mixture of silicon and zirconium oxides; impregnating anactive precious metal component, comprising platinum, palladium, or amixture thereof, onto the coated substrate; drying the coated substrate;and calcining the coated substrate, to prepare a sulfur-tolerantcatalytic system that may obtain a carbon monoxide conversion greaterthan 80% after continuous long term operation under high sulfur levelconditions.

In certain embodiments, the method of preparing a sulfur-tolerantcatalytic system comprises: impregnating an active precious metalcomponent, comprising platinum, palladium, or a mixture thereof, onto asulfur-tolerant support material, comprising a mixture of silicon andzirconium oxides, to form a slurry; coating a substrate, comprising aceramic material or a metal foil, with the slurry; drying the coatedsubstrate; repeating the coating and the drying as necessary; andcalcining the coated substrate, to prepare a sulfur-tolerant catalyticsystem that may obtain a carbon monoxide conversion greater than 80%after continuous long term operation under high sulfur level conditions.

In certain embodiments the coating may be applied using a washcoatingmethod.

In certain embodiments, the disclosure is directed to a method ofpreparing a sulfur tolerant catalytic system, comprising a catalyticmaterial, comprising active precious metal component present in anamount ranging from about 0.4 wt % to about 10 wt % based on totalcatalytic material composition, a sulfur-tolerant support present in anamount ranging from about 90 wt % to about 98 wt % based on totalcatalytic material composition, a substrate, and bulk ceria present inan amount ranging from about 0.5 wt % to about 10 wt % based on totalcatalytic material composition. In certain embodiments, thesulfur-tolerant catalytic system may have aluminum present in an amountof up to about 10 wt % based on total catalytic material composition.

In certain embodiments, the method of preparing a sulfur-tolerantcatalytic system comprises a catalytic material in a form of particlescomprising 90% cumulative undersize particle size from about 6micrometers to about 14 micrometers, or about 10 micrometers.

In certain embodiments, the disclosure is directed to a method forcontrolling carbon monoxide levels in an exhaust gas stream containinghigh sulfur levels comprising: providing a sulfur-tolerant catalyticsystem according to an embodiment of the disclosure; placing thesulfur-tolerant catalytic system in a stream containing carbon monoxideand high sulfur levels; and obtaining a carbon monoxide conversiongreater than 80% after continuous long term operation under high sulfurlevel conditions. The substrate may comprise a ceramic or a metal foil.In certain embodiments, the disclosure is directed to a method forcontrolling carbon monoxide levels in a stream devoid of sulfur.

In certain embodiments, the disclosure is directed to a method ofoxidizing carbon monoxide and/or controlling carbon monoxide levels in agas stream, the method comprising: providing a catalyst systemcomprising a catalytic material, comprising an active precious metalcomponent present in an amount ranging from 0.4 wt % to 10 wt % based ontotal catalytic material composition, a sulfur-tolerant support presentin an amount ranging from 90 wt % to 98 wt % based on total catalyticmaterial composition, a substrate, and bulk ceria present in an amountranging from 0.5 wt % to 10 wt % based on total catalytic materialcomposition. In certain embodiments, the catalytic system may comprisealuminum present in an amount of up to 10 wt % based on total catalyticmaterial composition. In certain embodiments, the aluminum has uniqueproperties, such as particle size and morphology, adapted to provideoptimal binding between catalytic material and the substrate. Thealuminum may be present in an amount sufficient to bind the catalyticmaterial to various substrates (e.g. metallic substrate).

In certain embodiments, the method for controlling carbon monoxidelevels in a stream comprises a sulfur tolerant catalytic system,comprising catalytic material in the form of particles having a 90%cumulative undersize particle size in the range of about 6 micrometersto about 14 micrometers, or about 10 micrometers.

The term “sulfur-tolerant” means that the physical and chemicalcharacteristics and/or performance in a stream containing high sulfurlevels remain unchanged or substantially unchanged when compared to thephysical and chemical characteristics and/or performance in a streamcontaining little or substantially no sulfur.

The term “high sulfur levels” refers to a stream having sulfur levels inthe range of about 0.1 ppm to about 500 ppm, or from about 50 ppm toabout 500 ppm.

The term “long term operation” refers to continuous operation for aperiod longer than about 1500 hours, or longer than 3300 hours, or about3300 hours, or from 1500 hours to 3300 hours.

The term “90% cumulative undersize particle size” refers to the relativeamount of particles having a size at or below the particular sizelisted. For example, 90% cumulative undersize particle size in the rangeof about 6 micrometers to about 14 micrometers, means that 90% of theparticles have a particle size ranging from about 6 micrometers to about14 micrometers or below.

The term “catalytic material” encompasses active precious metals and thesupport. This term refers to elements used to promote a desired chemicalreaction.

The term “catalytic system” encompasses the catalytic material and thesubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present disclosure, their nature,and various advantages will become more apparent upon consideration ofthe following detailed description, taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a flow chart illustrating a method for preparing asulfur-tolerant catalytic system according to an embodiment of thedisclosure;

FIG. 2 is a flow chart illustrating a method for preparing asulfur-tolerant catalytic system according to another embodiment of thedisclosure;

FIG. 3 is a flow chart illustrating a method for controlling carbonmonoxide levels in a stream containing high sulfur levels; and

FIG. 4 is a plot showing sustained long term catalyst performance of oneembodiment of the present disclosure in a stream containing high sulfurlevels.

FIG. 5 is a Raman spectra of the support utilized in sulfur-tolerantcatalytic systems according to embodiments of the disclosure.

DETAILED DESCRIPTION

The present disclosure is directed to a sulfur-tolerant catalyticsystem, methods of its preparation, and methods of its use in streamscontaining high sulfur levels. In one embodiment, the disclosure isdirected to a treatment of an exhaust stream of a power generationturbine to convert pollutants such as carbon monoxide (CO), volatileorganic compounds (e.g., aromatics, aldehydes, carboxylic acids, etc.),and NO_(x) abatements into less harmful compounds such as oxygen, carbondioxide and water vapor. Catalytic systems and methods of the presentinvention are suitable for treatment of various streams with high sulfurlevels, for instance, volatile organic compound streams from chemicalplants.

In one aspect of the disclosure, the sulfur-tolerant catalytic systemprovides an acceptable catalytic activity that is maintained overextended long term operations at high sulfur levels.

In certain embodiments, the disclosure is directed to a catalytic systemcomprising a catalytic material and a substrate, wherein the catalyticmaterial is coated on the substrate. The catalytic material comprisingan active precious metal component and a sulfur-tolerant supportmaterial. The active precious metal component comprising platinum,palladium, or mixtures thereof, and the sulfur-tolerant supportcomprising a mixture of silica and zirconia.

The sulfur-tolerant catalytic system disclosed herein may treat one ormore pollutants, such as ozone, hydrocarbons, volatile organic compounds(e.g., aromatics, aldehydes, carboxylic acids, etc.), carbon dioxide,carbon monoxide, nitrous oxides (e.g., nitric oxide and nitrogendioxide), or other pollutants. For example, the sulfur-tolerantcatalytic system may convert ozone to oxygen; carbon dioxide to water;carbon monoxide to carbon dioxide; or nitrous oxides to nitrogen ornitrate.

The active precious metal of the sulfur-tolerant catalytic systemdisclosed herein may be, e.g., platinum, palladium, rhodium, ruthenium,gold, silver, other precious metals, compounds containing the same andcombinations thereof.

In one embodiment, the active precious metal is a combination ofplatinum and palladium which may be derived from various precursory saltsolutions.

The support material may be a high surface area support material. Incertain embodiments, the support material has a surface area of at leastabout 100 m²/g; at least about 150 m²/g; at least about 200 m²/g; fromabout 150 m²/g to about 275 m²/g or from about 200 m²/g to about 250m²/g.

The surface area of the material may be determined by the BET(Brunauer-Emmett-Teller) method according to DIN ISO 9277:2003-05. Thespecific surface area is determined by a multipoint BET measurement inthe relative pressure range from 0.05-0.3 p/p₀.

The material utilized as the sulfur-tolerant support material can be arefractory oxide or any other suitable material. For example, thesupport material may comprise, e.g., ceria, lanthana, alumina, titania,silica, zirconia, carbons, metal organic framework, clay, zeolites,other refractory oxides, other suitable materials, and combinationsthereof.

In one embodiment, the sulfur-tolerant support material is selected froma group comprising silica, zirconia, and combinations thereof. In oneembodiment, the support material is a combination of silica and zirconiawhich may be derived from silicon oxide and zirconium oxideco-precipitated or comingled mixture.

The silicon oxide to zirconium oxide=weight ratio (w/w) may range fromabout 1:4 to about 1:98.

In another embodiment, the active precious metal component of thecatalytic system may be in an amount, e.g., ranging from about 0.1 wt %to about 2.0 wt %, about 0.1 wt % to about 1.2 wt %, or about 0.1 wt %to about 0.6 wt % based on total weight of the catalytic system, orranging from about 0.4 wt % to about 10 wt %, about 0.4 wt % to about3.0 wt %, or about 0.4 wt % to about 1.5 wt % based on total weight ofthe catalytic material. In certain embodiments, platinum may be presentfrom about 0.1 wt % to about 2.0 wt % of a total weight of catalyticsystem. In certain embodiments, platinum may be present up to about 2.0wt % of a total weight of catalytic system. In certain embodiments,platinum may be present from about 0.4 wt % to about 5.0 wt %, fromabout 0.4 wt % to about 3.0 wt %, or from about 0.4 wt % to about 1.5 wt% of a total weight of catalytic material. In certain embodiments,palladium may be present up to about 5.0 wt %, up to about 3.0 wt %, orup to about 1.5 wt % of a total weight of catalytic material. In certainembodiments, platinum may be the only precious metal component in thecatalytic material. In certain embodiments, the catalytic material maycomprise a plurality of active precious metal components.

In certain embodiments of the disclosure, a portion of the catalyticmaterial is in amorphous form. In certain aspects, at least 50%, atleast 60%, at least 75% or at least 85% of the catalyst is in amorphousform. For instance, in one embodiment, the support may be at least 50%,at least 60%, at least 75%, at least 85%, or 100% amorphous.

The catalytic system of the present invention may be used independent ofother materials to treat the generation turbine exhaust gas stream orcan be combined with other materials. Similarly, the catalytic system ofthe present invention may be used independently to treat a volatileorganic compound stream from a chemical plant or may be combined withother materials. In one embodiment, the catalytic system comprises acatalytic material washcoated onto a substrate. The substrate may be,e.g., a ceramic or a metal foil.

In certain embodiments, the sulfur-tolerant catalytic system of thepresent disclosure may include an acid additive. The acid additive maybe an organic acid or any other suitable acid. For example, the acidadditive may be selected from the group consisting of acetic acid ornitric acid, and a combination thereof.

The coating of the precious group metals on the support may be of anysuitable thickness, e.g., from about 10 micrometers to about 150micrometers.

In one embodiment, a cumulative pore volume of the sulfur-tolerantcatalytic system is at least about 0.2 mL/g, from about 0.2 mL/g toabout 1.2 mL/g, or about 0.7 mL/g. In other embodiments, an average poreradius of the sulfur-tolerant catalytic system is from about 1.5nanometers to about 20 nanometers, from about 1.8 nanometers to about 7nanometers, or about 2 nanometers, or about 7 nanometers.

In some embodiments, the sulfur tolerant catalytic system is directed toa physical mixture of active precious metal oxide catalyst particles andhigh surface area sulfur-tolerant support particles having separatedomains of metal oxide and support and functioning independently ascatalyst and aging protection respectively.

In other embodiments, the catalytic system comprises an alloy of activeprecious metal oxide catalysts and high surface area sulfur-tolerantsupport resulting in inseparable functionality for each material fromthe other.

In some embodiments, the catalytic system comprises a high surface areasubstrate particle in surface contact either within the pore structureand/or externally with small (<100 nm) domains of active precious metaloxides such that separate domains of metal oxide can functionindependently as catalyst and are provided protection from agingmechanisms within the substrate (e.g., by coating a substrate with asulfur-tolerant support).

In other embodiments, a high surface area substrate particle isexternally coated with a porous shell structure of a catalytic materialsuch that the catalyst function is external to the sulfur-tolerantsupport providing a high catalytic surface area interior to thecomposite particle.

In other embodiments, a high surface area substrate encompasses anactive precious metal oxide particle in a coating layer such that themetal oxide particle is entirely surrounded by a protective high surfacearea sulfur-tolerant support material.

In some embodiments, a material promoting oxygen storage may be added tothe catalytic system such as, for example, bulk ceria. In someembodiments, other types of binders or oxygen storage materials may beused, such as silicon or zirconium based binders, e.g. colloidal silica,colloidal zirconia, zirconium nitrate or acetate solution, orcombinations thereof, which may be present in a range of about 1%, about2%, about 3%, about 4%, or about 5% to about 6%, about 7%, about 8%,about 9%, or about 10% by mass of the washcoat.

Method for Preparing a Sulfur-Tolerant Catalytic System

The present disclosure is also directed to methods of preparing asulfur-tolerant catalytic system comprising coating a catalytic materialonto a substrate, wherein the catalytic material comprises activeprecious metals, e.g., a mixture of platinum and palladium, and asulfur-tolerant support, e.g., a mixture of silicon and zirconiumoxides.

In other embodiments, a method of preparing a sulfur-tolerant catalyticsystem comprises coating a sulfur tolerant support onto a substrate,followed by impregnating active precious metals onto the coatedsubstrate, wherein the active precious metals comprise, e.g., platinum,palladium, or a mixture thereof, and the sulfur-tolerant supportcomprises, e.g., a mixture of silica and zirconia.

In certain aspects, the coating may be done by, e.g., washcoating,spraying, powder coating, dip coating, or any equivalent method ofcoating. The catalytic system may further comprise other agents such assilicon, zirconium, or aluminum based binders, e.g. colloidal silica,colloidal zirconia, zirconium nitrate or acetate solution, orcombinations thereof, which may be present in a range of about 1%, about2%, about 3%, about 4%, or about 5% to about 6%, about 7%, about 8%,about 9%, or about 10% by mass based on the washcoat.

FIG. 1 is a flow chart illustrating a method 100 of preparing asulfur-tolerant catalytic system according to an embodiment of thedisclosure, the sulfur-tolerant catalytic material comprising acatalytic material (comprising an active precious metal component) and asulfur-tolerant support material coated onto a substrate. In oneembodiment, the catalytic material is prepared in accordance with block102, for example, in the form of a slurry having target amounts ofactive precious metal salts (e.g., acetate, nitrate, carbonate, sulfatebased salts, or potassium permanganate) mixed with a sulfur-tolerantsupport material (e.g., zirconia, silica, or combinations thereof). Theactive precious metals may be impregnated sequentially to incipientwetness on the sulfur-tolerant support material. Water may be added totarget percent slurry solids. For example, the target percent slurrysolids may be in the range of from about 20%, about 25%, about 30%,about 35% to about 40%, about 45%, or about 50%. The catalytic materialmay be in a form of particles and may be milled to obtain a desiredparticle size. The desired 90% cumulative undersize particle size maybe, for example from about 1, about 2, about 3, about 4, about 5, orabout 6 to about 7, about 8, about 9, about 10, about 11, about 12,about 13, about 14, or about 15 micrometers. For instance, the 90%cumulative undersize particle size may be about 12 micrometers.

In certain embodiments, catalytic material prepared in block 102 may becoated onto a substrate in accordance with block 104. The substrate maycomprise, for example, a monolithic catalyst substrate made of ceramicor metal. The substrate may comprise varying channel cross sectionshapes, for example, honeycomb, square, sinusoidal, triangular,hexagonal, trapezoidal, or round The cell density of the substrate mayrange, for example, between about 64 to about 600 cells per square inch(cpsi). The wall thickness of the substrate may range from about 48 μmto about 380 μm

The coated substrate is subsequently dried pursuant to block 106. Thedrying may be performed for a period ranging, for example, from about 1minute, 5 minutes, 10 minutes, 15 minutes, 30 minutes, 1 hours, 2 hours,3 hours, 4 hours, or 5 hours to about 8 hours, 10 hours, 13 hours, 16hours, 24 hours, 48 hours, or 72 hours. The drying may be performed at atemperature ranging, for example, from about 105° C., about 150° C.,about 200° C., or about 250° C. to about 300° C., about 400° C., about500° C., about 550° C., or about 600° C., at a convection air dryer or asimilar conventional drying method or apparatus. The coating accordingto block 104 and the drying according to block 106 may be repeated asmany times as necessary to obtain a target loading concentration, forexample, once, twice, or three times. The target loading concentrationmay range, from example, from about 10 g/l, about 15 g/l, about 20 g/l,or about 30 g/l to about 50 g/l, about 75 g/l, about 100 g/l, about 120g/l, or about 150 g/l. In one embodiment, the target loading of theslurry onto the substrate may be about 100 g/l.

Any subsequent coating or drying may have the same conditions as thoseof the initial coating and drying, or may vary from the conditions ofthe initial coating and drying. For example, an initial slurry ofcatalytic material to be coated may contain about 40% slurry solids anda subsequent slurry of catalytic material to be coated may contain about30% slurry solids, or both the initial and the subsequent slurry ofcatalytic material to be coated may contain the same percent slurrysolids of about 35%. Another example may be where a substrate coatedonce is dried at 110° C. for about one hour, and the second coat isdried at 110° C. for about four hours, or where each of the coats aredried for the same time period at the same temperature.

The dried substrate may be subsequently calcined pursuant to block 108.The calcination may be performed in a muffle furnace or in a similarconventional calcination method or apparatus. Block 108 may follow acalcination cycle comprising, for example, ramping the temperature fromabout 110° C., about 150° C., about 200° C., or about 250° C. to about300° C., about 400° C., about 500° C., about 550° C., or about 600° C.at a rate of about 1° C./min, about 2° C./min, about 3° C./min, about3.7° C./min, or about 4° C./min, soaking at about 550° C. for about one,two, or three hours, and then cooling to about 110° C., about 150° C.,about 200° C., or about 250° C. The temperatures, durations, and ratesof the calcination in the above-referenced example should not beconstrued as limiting.

FIG. 2 is a flow chart illustrating a method 200 for preparing asulfur-tolerant catalytic system according to another embodiment of thedisclosure, wherein a sulfur-tolerant support may be coated onto asubstrate, the coated substrate is dried and calcined as necessary,followed by post impregnation of an active precious metal component ontothe coated substrate, drying and calcining. In certain embodiments ofmethod 200, a sulfur-tolerant support is coated onto a substrate inaccordance with block 202. The substrate may comprise materials, shape,cell density, wall thickness, or pressure drop through it as describedabove in method 100.

The sulfur-tolerant support coating may be prepared in a form of slurryhaving target amounts of sulfur-tolerant support. The sulfur-tolerantsupport may be e.g., silica, zirconia, or mixtures thereof, wherein amixture of silica and zirconia may comprise, for example, silica andzirconia mixed oxides, co-mingled silica and zirconia particles,co-precipitated silica and zirconia particles, silica particles coatedwith zirconia, zirconia particles coated with silica and othervariations. The sulfur-tolerant support present in the slurry may range,for example, from about 80 wt %, about 85 wt %, about 90 wt %, or about92 wt % to about 94 wt %, about 96 wt %, about 98 wt %, or about 99 wt %based on the total weight of the solids in the slurry.

In block 204, the coated substrate is dried and calcined as necessarybefore post-impregnation with an active precious metal component. Inblock 206, a solution having target levels of active precious metalsalts (e.g., acetate, nitrate, carbonate, sulfate based salts, orpotassium permangante) is mixed with the coated substrate. The activeprecious metal component may be e.g., platinum, palladium or a mixturethereof. The target level of platinum in the slurry may range, forexample, from about 0.1 wt % to about 20 wt %, from about 1 wt % toabout 10 wt %, from about 2 wt % to about 5 wt %, or about 3 wt %platinum based on the total weight of the solution. The target level ofpalladium in the slurry may range, for example, from about 0.1 wt % toabout 20 wt %, from about 1 wt % to about 10 wt %, from about 2 wt % toabout 5 wt %, or about 3 wt % palladium based on the total weight of thesolution. The active precious metal component may be applied onto thecoated substrate through the method of impregnation, washcoating and asimilar equivalent method. Water may be added to target percent slurrysolids. For example, the target percent slurry solids may be in therange from about 20%, about 25%, about 30%, about 35% to about 40%,about 45%, or about 50%. The slurry may comprise particles which may bemilled to obtain a desired particle size. The desired 90% cumulativeundersize particle size may be, for example, from about 1, about 2,about 3, about 4, about 5, or about 6 to about 7, about 8, about 9,about 10, about 11, about 12, about 13, about 14, or about 15micrometers. For instance, the 90% cumulative undersize particle sizemay be about 10 or about 12 micrometers. Subsequently, in block 208, thecoated substrate impregnated with an active precious metal component maybe dried as described for drying block 106. Coating and drying accordingto blocks 206 and 208 may be repeated as necessary, either with varyingconditions or as exact duplicates. The dried substrate may then becalcined in accordance with block 210 following a predeterminedcalcination cycle.

In certain embodiments, the catalytic material is a physical mixture ofcatalytic material particles and high surface area substrate particles,wherein the catalytic material particles are impregnated onto highsurface area substrate particles. In other embodiments, the disclosureis directed to a physical mixture of active precious metal oxideparticles and substrate particles, wherein the substrate particles arealready coated with high surface area sulfur-tolerant support particlesand the active precious metal oxide particles are post impregnated ontothe coated substrate particles. The various particles may functionindependently as catalyst, aging protection, and sulfur tolerance.

In certain embodiments, the catalytic material is an alloy of activeprecious metal oxide and high surface area sulfur-tolerant support,wherein the active precious metal oxide is impregnated onto a highsurface area sulfur-tolerant support. The function of the variousmaterials is inseparable from each other.

In certain embodiments, the catalytic material is a high surface areasupport particle which is in surface contact either within the porestructure and/or externally with small (<100 nm) domains of activeprecious metal oxide catalysts such that separate domains of activeprecious metal oxides can function independently as catalysts and areprovided protection from aging mechanisms within the support material.

Method for Controlling Carbon Monoxide Content

One aspect of the present disclosure is directed to a method of using asulfur tolerant catalytic system in a stream containing high sulfurlevels to oxidize pollutants such as carbon monoxide (CO), volatileorganic compounds (e.g., aromatics, aldehydes, carboxylic acids, etc.),and NO_(x) abatements into less harmful compounds such as oxygen, carbondioxide and water vapor.

In another aspect, a sulfur-tolerant catalytic system comprises acatalytic material comprising an active precious metal component and asulfur-tolerant support material impregnated with the active preciousmetal component, such that the catalytic material, when coated onto asubstrate and contacted with a stream having an initial carbon monoxideconcentration, converts carbon monoxide within the stream such that afinal carbon monoxide concentration of the stream is reduced by greaterthan 70%, greater than 75%, greater than 80%, greater than 85%, greaterthan 90%, or greater than 95% of the initial carbon monoxideconcentration after the sulfur-tolerant catalytic system is contactedwith the airstream.

In another aspect, a sulfur-tolerant catalytic system comprises asulfur-tolerant support material coated on a substrate and an activeprecious metal component impregnated on the coated substrate, such thatthe catalytic system, when contacted with a stream having an initialcarbon monoxide concentration, converts carbon monoxide within thestream such that a final carbon monoxide concentration of the stream isreduced by greater than 70%, greater than 75%, greater than 80%, greaterthan 85%, greater than 90%, or greater than 95% of the initial carbonmonoxide concentration after the catalytic system is contacted with thestream.

The initial carbon monoxide concentration ranges from about 5 ppm, about10 ppm, about 25 ppm, about 50 ppm, or about 100 ppm to about 200 ppm,about 500 ppm, about 1000 ppm, about 1500 ppm, about 2000 ppm, about2500 ppm, about 3000 ppm, about 3500 ppm, or about 4000 ppm. The spacevelocity of the stream may range from about 10,000 hr⁻¹, about 25,000hr⁻¹, about 50,000 hr⁻¹, about 60,000 hr⁻¹, or about 100,000 hr⁻¹ toabout 150,000 hr⁻¹, about 200,000 hr⁻¹, or about 300,000 hr⁻¹, and atemperature of the stream is maintained within a range of about 200° C.,about 230° C., about 260° C., or about 300° C. to about 450° C., about500° C., about 550° C., or about 600° C.

In one embodiment, the catalytic material, when coated onto a substrateand contacted with a stream having an initial carbon monoxideconcentration, is adapted to convert carbon monoxide within the streamsuch that a final carbon monoxide concentration of the airstream isreduced by greater than 70%, greater than 75%, greater than 80%, greaterthan 85%, greater than 90%, or greater than 95% of the initial carbonmonoxide concentration after the sulfur-tolerant catalytic system iscontacted with the stream. In some embodiments, the final carbonmonoxide concentration of the stream is reduced by greater than 60% ofthe initial carbon monoxide concentration.

In one embodiment, the catalytic performance of a sulfur-tolerantcatalytic system according to the disclosure remains acceptable andconsistent after continuous operation for at least 1500 hours. In oneembodiment, the catalytic performance of a sulfur-tolerant catalyticsystem according to the disclosure remains acceptable and consistentafter continuous operation for at least 3300 hours. In one embodiment,the catalytic performance of a sulfur-tolerant catalytic systemaccording to the disclosure remains acceptable and consistent aftercontinuous operation for at least 5000 hours.

The following examples are set forth to assist in understanding theinvention and should not, of course, be construed as specificallylimiting the invention described and claimed herein. Such variations ofthe invention, including the substitution of all equivalents now knownor later developed, which would be within the purview of those skilledin the art, and changes in formulation or minor changes in experimentaldesign, are to be considered to fall within the scope of the inventionincorporated herein.

ILLUSTRATIVE EXAMPLES Example 1: Sulfur-Tolerant Catalytic SystemPreparation

Platinum A (16.62% Pt) and Palladium nitrate salt solutions (20.24% Pd)were impregnated sequentially to incipient wetness on a silica-zirconiasupport material. Water was then added to the impregnated powder totarget 45% slurry solids. The slurry was then passed through an EMIhorizontal continuous mill until the d90 cumulative undersize particlesize was 10 μm. Bulk ceria was added and the slurry was mixed under lowshear mixing until homogenized. A ceramic honeycomb core was coated withthe slurry mixture at a slurry solids content of approximately 27%. Thecoated honeycomb was dried at 110° C. for one hour in a convection airdryer prior to recoating a second time to target loading of 105 g/ltotal washcoat. The honeycomb was then dried again at 110° C. for fourhours. The dried honeycomb was transferred to a muffle furnace at 110°C. for the following calcination cycle: ramp from 110° C. to 550° C. at3.7° C./min, then soak at 550° C. for two hours, then cool to 110° C.for dry weight. The target washcoat concentration was as follows:

-   -   Pt, as metal: 0.5%    -   Pd, as metal: 0.5%    -   10% silica on zirconia: 98.0%    -   Ceria: 1.0%

Example 2: Sulfur-Tolerant Catalytic System Preparation (ContainingAluminum)

Zirconyl nitrate solution and boehmite aluminum oxide hydroxide wereadded to water. A 10% silica on zirconia support material was added totarget 40% slurry solids. The slurry was then passed through an EMIhorizontal continuous mill until the d90 cumulative undersize particlesize was 10 μm. Bulk ceria was added and the slurry was mixed under lowshear mixing until homogenized. Zirconyl acetate solution was added tothe slurry and a Fe—Cr—Al corrugated foil was coated with the slurrymixture at a slurry solids content of approximately 30%. The coated foilwas dried at 110° C. for one hour in a convection air dryer prior torecoating a second time. Again the coated foil was dried at 110° C. forone hour in a convection air dryer prior to recoating a third time to atarget loading of 28 mg/in². The dried foil was transferred to a mufflefurnace at 110° C. for the following calcination cycle: ramp from 110°C. to 550° C. at 3.7° C./min, then soak at 550° C. for two hours, thencool to 110° C. for dry weight. The target washcoat concentration was asfollows:

-   -   10% silica on zirconia: 86.6%    -   Zirconia (as nitrate and acetate): 7.4%    -   Alumina (as boehmite aluminum oxide hydroxide): 5.0%    -   Ceria: 1.0%    -   Tetraamine platinum hydroxide solution was diluted with        deionized water and then sprayed onto to the calcined washcoat        on the foil until the washcoat was completely saturated. The        target platinum loading was 1.0 wt %. The wet foil was dried at        110° C. for one hour. The dried foil was transferred to a muffle        furnace at 110° C. for the following calcination cycle: ramp        from 110° C. to 550° C. at 3.7° C./min, then soak at 550° C. for        two hours, then cool to 110° C. for dry weight.

TABLE 1 Catalytic System Morphological Properties Active preciousSurface Pore Avg. metal Area volume Pore dispersion (BET), (BJH), RadiusSample (XPS) m²/g mL/g (BJH), nm Example 1 Pt: 0.48 210 0.7 6 Pd: 0.48Example 2 Pt: 0.5 195 0.5 6 (with Aluminum)

Example 3: Carbon Monoxide Conversion Testing Method

FIG. 3 is a flow chart illustrating a method for controlling carbonmonoxide levels in a stream containing high sulfur levels (e.g., using acatalyst prepared according to Example 1 and corresponding to blocks302-306). In block 308, the resulting sulfur-tolerant catalytic systemis contacted with a stream containing carbon monoxide, high sulfurlevels, and other pollutants in order to oxidize the pollutants intoless harmful compounds. The sulfur-tolerant catalytic system is operatedin a stream containing high level of sulfur continuously for at leastabout four and a half months, in accordance with block 310. Theresulting performance of a catalytic system, according to an embodimentof the disclosure, over the extended period of time of four and a halfmonths is shown in FIG. 4 . According to FIG. 4 , the carbon monoxideconversion remains about 80% or greater regardless of whether thesulfur-tolerant catalyst used is fresh, has been operating for 1,249hours (about 52 days) or for 3,334 hours (about 139 days).

XPS measurements were conducted using a K-Alpha™⁺x-ray photoelectronspectrometer system (Thermo Scientific) with an aluminium K-α X-raysource. Powder samples were loaded onto carbon tape and outgassed for 2hours prior to analysis. After an initial survey scan of the samplesurface from 0-1350 eV, targeted high resolution scans of identifiedelements were conducted using a constant pass energy of 40.0 eV. Thebinding energies were referenced to the adventitious Cis peak, 284.8 eV.Shirley background and mixed Gaussian-Lorentzian line shapes were usedto fit the resulting XPS spectra. Relative atomic percentages were thendetermined using the fitted peak data and sensitivity factors of eachelement (provided by Avantage software).

The pore structure of the supported catalyst, including both the porevolume and pore width, as well as surface area of the catalysiscompositions were measured using a Micromeritics® TriStar 3000 Seriesinstrument. Samples were prepared using an initial degassing cycle underN₂ with a 2 hour ramp rate up to 300° C. and a 4 hour soak time at 300°C. For surface area values, a 5 point BET measurement was used withpartial pressures of 0.08, 0.11, 0.14, 0.17, and 0.20. Cumulative porevolume and average pore radius measurements were obtained from a BJHmultipoint N₂ desorption/adsorption isotherm analysis using only poreswith radii between 1.0 nm and 30.0 nm.

Example 4: Raman Spectra Analysis of Support

Three samples were analyzed using Raman Spectra, namely a pure zirconiasample, a 10% silica on zirconia sample obtained during development, anda 10% silica on zirconia sample obtained in the pilot phase. The resultsare summarized in FIG. 5 .

Raman spectra were collected on a Reneshaw InVia Raman microscope with488 nm laser as the excitation source. A Leica N PLAN microscope/50×objective lens was used to focus the 488 nm laser beam on the samplesurface at 100% in power usage. Raman spectra were collected underambient condition.

The control sample (pure zirconia) showed a monoclinic crystal systemphase. The two 10% silica on zirconia samples did not show crystallinestructures as compared to the control. However, the 10% silica onzirconia sample obtained during development showed a sharp peak at 460cm⁻¹, which is very close to 473 cm⁻¹ peak in the reference sample. Thispeak may be due to distorted O-O vibration in zirconia by silica. Thisassumption should not be construed as limiting.

For simplicity of explanation, the embodiments of the methods of thisdisclosure are depicted and described as a series of acts. However, actsin accordance with this disclosure can occur in various orders and/orconcurrently, and with other acts not presented and described herein.Furthermore, not all illustrated acts may be required to implement themethods in accordance with the disclosed subject matter. In addition,those skilled in the art will understand and appreciate that the methodscould alternatively be represented as a series of interrelated statesvia a state diagram or events.

In the foregoing description, numerous specific details are set forth,such as specific materials, dimensions, processes parameters, etc., toprovide a thorough understanding of the present invention. Theparticular features, structures, materials, or characteristics may becombined in any suitable manner in one or more embodiments. The words“example” or “exemplary” are used herein to mean serving as an example,instance, or illustration. Any aspect or design described herein as“example” or “exemplary” is not necessarily to be construed as preferredor advantageous over other aspects or designs. Rather, use of the words“example” or “exemplary” is intended to present concepts in a concretefashion. As used in this application, the term “or” is intended to meanan inclusive “or” rather than an exclusive “or”. That is, unlessspecified otherwise, or clear from context, “X includes A or B” isintended to mean any of the natural inclusive permutations. That is, ifX includes A; X includes B; or X includes both A and B, then “X includesA or B” is satisfied under any of the foregoing instances. In addition,the articles “a” and “an” as used in this application and the appendedclaims should generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. Reference throughout this specification to “an embodiment”,“certain embodiments”, or “one embodiment” means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment. Thus, the appearancesof the phrase “an embodiment”, “certain embodiments”, or “oneembodiment” in various places throughout this specification are notnecessarily all referring to the same embodiment.

The term “about”, when referring to a physical quantity, is to beunderstood to include measurement errors within, and inclusive of 2%.For example, “about 100° C.” should be understood to mean “100±1° C.”.

The present invention has been described with reference to specificexemplary embodiments thereof. The specification and drawings are,accordingly, to be regarded in an illustrative rather than a restrictivesense. Various modifications of the invention in addition to those shownand described herein will become apparent to those skilled in the artand are intended to fall within the scope of the appended claims.

What is claimed is:
 1. A method comprising: providing a catalytic system, wherein the catalytic system comprises: a catalytic material comprising: an active precious metal component comprising platinum; and a sulfur-tolerant support material comprising silica and zirconia mixture; and a substrate having the catalytic material coated thereon; placing the catalytic system in a stream containing carbon monoxide and high sulfur levels of at least 0.1 ppm of sulfur; and aging the stream containing the high sulfur levels with the catalytic system, wherein the aging results in a carbon monoxide conversion greater than 80% after aging the stream for 1500 hours.
 2. The method of claim 1, wherein at least 50% of the sulfur-tolerant support material is amorphous.
 3. The method of claim 1, wherein the carbon monoxide conversion is greater than 80% after aging the stream for 3300 hours.
 4. The method of claim 1, wherein the substrate comprises a ceramic or a metal foil.
 5. The method of claim 1, wherein the stream containing high sulfur levels comprises from 0.1 to 500 ppm of sulfur.
 6. The method of claim 1, wherein the platinum is present in an amount from 0.4 wt % to 5.0 wt % of a total weight of the catalytic material.
 7. The method of claim 1, wherein the active precious metal component further comprises palladium, wherein the palladium is present in an amount of from about 0.1 wt % to 5.0 wt % of a total weight of the catalytic material.
 8. The method of claim 1, wherein the sulfur-tolerant support is present in an amount from 90 wt % to 98 wt % of a total weight of the catalytic material.
 9. The method of claim 1, wherein the silica to zirconia ratio in the sulfur-tolerant support material ranges from 1:4 to 1:98.
 10. The method of claim 1, wherein the catalytic system further comprises bulk ceria.
 11. The method of claim 10, wherein the bulk ceria is present in an amount from 0.5 wt % to 10 wt % of a total weight of the catalytic material.
 12. The method of claim 1, wherein the catalytic material is in a form of particles, and wherein 90% of the particles have a particle size ranging from about 6 micrometers to about 14 micrometers.
 13. A method comprising: providing a catalytic system, wherein the catalytic system comprises: a catalytic material comprising: an active precious metal component comprising platinum; and a sulfur-tolerant support material comprising silica and zirconia mixture, wherein the silica to zirconia ratio in the sulfur-tolerant support material ranges from 1:4 to 1:98; and a substrate having the catalytic material coated thereon; placing the catalytic system in a stream containing carbon monoxide and high sulfur levels of at least about 0.1 ppm of sulfur; and aging the stream containing the high sulfur levels with the catalytic system, wherein the aging results in a carbon monoxide conversion greater than 80%.
 14. A method comprising: providing a catalytic system, wherein the catalytic system comprises: a catalytic material comprising: an active precious metal component comprising platinum; and a sulfur-tolerant support material comprising silica and zirconia mixture, wherein the catalytic material is in the form of particles, and wherein 90% of the particles have a particle size ranging from about 6 micrometers to about 14 micrometers; and a substrate having the catalytic material coated thereon; placing the catalytic system in a stream containing carbon monoxide and high sulfur levels of at least about 0.1 ppm of sulfur; and aging the stream containing the high sulfur levels with the catalytic system, wherein the aging results in a carbon monoxide conversion greater than 80%. 